The present invention relates to a plasma display system having a plasma display panel for use as a display, particularly as a thin display panel in which the energy of a ultraviolet ray excites phosphors to obtain visible lights.
A plasma display panel (hereinafter referred to as the PDP) is made of small plasma light emitting cells each of which is enclosed by barrier ribs, a face panel, and a back plate at each of crossing portions of stripe data line electrodes and scanning line electrodes crossing like a matrix. The plasma light emitting cells have a phosphor corresponding to one of three primary colors provided thereinside. If a plasma is discharged as selected by the data line electrode and the scanning line electrode, the plasma generates an ultraviolet ray. The ultraviolet ray excites the phosphor to emit a light, thereby forming a picture element of the plasma display system.
In the Japanese Patent Application Laid-Open (TOKU-KAI-SHO) No. 61-24126 is disclosed a first prior art that color of the substance used for the barrier ribs forming the cells is changed from white to black so that absorption of the lights emitted by the phosphors excited by the ultraviolet ray is made as little as possible to increase the luminance of the above-described plasma display panel (PEP). The first prior art uses the substance containing no black pigment for forming the barrier ribs to increase the reflection factor of the lights to reflect the lights emitted by the phosphors effectively.
Also, in the Japanese Patent Application Laid-Open (TOKU-KAI-SHO) Nos. 59-36280 and 61-6151 is disclosed a second prior art that the cells have optical filters of inorganic substances attached to the openings thereof for color lights to increase the color purity and contrast of the PDP. The second prior art having the optical filters inside the light emitting cells can have a desired thickness of the face panel since the thickness does not cause such errors of phenomena that parts of the light do not pass the filter and passes the filter of different color.
The above-mentioned first prior art can increase the reflection factor to increase the luminance since the color of the substance used for the barrier ribs forming the cells is white. However, the first prior art has the disadvantage that the color purity is decreased since the substance reflects the lights of all wavelengths and if the spectra of the lights emitted by the phosphor are not of a single wavelength, the substance reflects the lights of undesired wavelengths. The first prior art also has the disadvantage that any possible coming external light causes deteriorations of characteristic performance, such as decrease of contrast, not taking into account the deteriorations of optical characteristic performance. The first prior art further has the disadvantage that the substance cannot always reflect the ultraviolet ray for exciting the phosphor effectively although reflecting the visible lights.
The above-mentioned second prior art is ideal in the principle that as described above, thickness of the face panel causes no error. However, the second prior art has the disadvantage that as a realistic problem, the filter has to be made of the substance the characteristics of which cannot be changed by ultraviolet ray since the filter put in the light emitting cell is always exposed to strong ultraviolet ray. The second prior art also has the disadvantage that the filter has to endure the high-temperature heat process of 500 to 600.degree. C. unavoidable for fabrication of the panel since the filter is attached to the face panel. The second prior art further has the disadvantage that the substance discharging undesired gases is impractical since the substance forming the filter is put in the cell. For those reasons, the substance for the filter is so limited as to meet the optical characteristics. The filter is made of the inorganic substance in the current situation, but is inferior to the ones of organic substances used in the CCD employed widely as image device and liquid crystal display panel. However, the organic substance filters cannot be currently treated in the high-temperature process so that the PDP cannot make full use of the excellent optical characteristics of the organic substance filter.
Also, the prior plasma display panels have the disadvantage that the face panel for feeding out the emitted light is made usually of a simple flat glass and is not shaped in view of directivity of the output light. For the reason, the prior plasma display panels cannot have high efficiency of the output light where wide directivity is not always needed.